Engineering is generally considered to be the worst profession in terms of making gold. While in my opinion it is the most enjoyable profession to have due to the large number of unique items you can make the fact that most of the items made by engineers can only be used by other engineers means that there is no market whatsoever for most of the items you can make.
1) You can make cool items with unique abilities.
2) Engineering is a fun profession to have.
1) You have VERY few items you can make for any profit whatsoever.
2) Welcome to the poorhouse!
My advice on engineering:
If you want to have fun and have some gold to spare pick up this profession. A lot of the items have unique abilities and it really is a very fun profession to have. If, on the other hand, you want to choose a profession that will MAKE you gold avoid engineering like the plague until you have all other professions.
Recipes of Note:
1) Pets such as the Mechanical Squirrel and Lifelike Mechanical Toad can be sold for a profit.
2) The hog or chopper motorcycle usually sells for a profit.
1) If you have a Wormhole Generator: Northrend make sure to use it whenever it is off of its cooldown. Very rarely you will get the option to go to "underground". If you get the opportunity choose this as it will take you to a rare recipe vendor that is only reachable by these means.
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The Power Word: Gold Guide Free is Copyright © 2011 Jim Younkin. Guide contributors include Bangkok Bill and fluxdada.